Dead spacethe air within the respiratory tract that never reaches the alveoli within the lungs and so does not undergo gaseous exchange |
Deaminationthe breakdown of excess amino acids in the liver, whereby the amine group is removed and converted to ammonia and eventually urea before excretion |
Deciduous dentitionteeth seen in the young animal soon after birth. These are shed after a few months and are replaced by the permanent teeth. |
Defecationact of passing feces from the rectum |
Definition (radiographic)the quality of the radiograph which is affected by density, contrast and sharpness |
Deglutitionthe act of swallowing |
Density (radiographic)the degree of blackening of the radiograph |
Dermal papillastructure situated at the base of the hair follicle containing nerves and blood vessels, which supply nutrients necessary for hair growth |
Dermislayer of dense connective tissue lying beneath the epidermis |
Desiccationthe process of losing moisture or “drying out” when exposed to air |
Detergenta chemical that disperses and removes soil, organic material and greasy residue from surfaces as well as reducing surface tension and increase the penetrating ability of water. This is a process that is important in allowing disinfectants to penetrate the pathogens underneath. Some disinfectants have their own detergent properties (eg the halogens – bleach and iodine, quaternary ammonium compounds). |
Developera chemical solution which converts exposed silver bromide crystals into silver metal within the emulsion during processing |
Diarrhoeaproduction of faeces that contain an excess amount of water |
Diastemaa space between teeth. There is a natural space in the jaw of rodents and herbivores where canine teeth would be found in other species. |
Diastolerelaxation stage of the cardiac cycle. The term applies to both atrial and ventricular relaxation. |
Diffusionthe net movement, as a result of random motion of its particles, of a substance from an area of high concentration to an area of low concentration |
Digestionthe process by which food materials are broken down into small soluble chemical units |
Dilated pupilsDilated pupils (mydriasis) are when the black center of your eyes are larger than normal. The condition may be caused by dilating eye drops from an eye exam, the side effects from a drug/medication or traumatic injury. |
Diploid cellscells with the full number of chromosomes, each in pairs. These include most cells within the animal’s body. |
Diploid numberthe number of chromosomes (2n) found in the nucleus of all cells except gametes which are haploid cells |
Disinfectanta chemical used to control, prevent and destroy pathogens present on inanimate objects - although it is not usually active against bacterial spores. The process does not necessarily kill all micro-organisms, but reduces then to a level acceptable for a defined purpose, for example a level which is considered not harmful to health. (Note, the difference between “disinfectants” and “antiseptics” which are applied to living tissues.) |
Disinfectionthe removal or inactivation of pathogenic micro-organisms but not necessarily of bacterial spores |
Disinhibitedto loose inhibitions and become exited |
Diuresisincreased amount of urine produced |
Diureticsdrugs used to increase the production of urine by the kidneys and so reduce water retention in the body |
DNA |
DNA gyrase |
DNA polymerase |
Dominant genea gene whose characteristics are always present in the phenotype, in homozygous and heterozygous individuals. It is represented with a capital letter, e.g. B. |
Dosemetera device for monitoring exposure to X-rays |
Drug scheduleclassification of drugs within the Misuse of Drugs Regulations 2001 |
Dry matterfood residue after being heated to remove all the water |
Dwarfismsmaller than normal size |
Dysecdysisabnormal shedding of the skin of reptiles |
Dysphagiadifficulty swallowing |
Dyspnoeadifficulty breathing |
Dystociadifficult parturition; difficulty giving birth |
Dysuriadifficulty in passing urine |